The ability to dissect a sample for analysis is an important tool in examining biological samples and non-biologic material. In medical research, tissue microdissection has become an important tool for the discovery of molecular phenomena that distinguish between the normal and abnormal development of organisms and tissues.
Other research areas, unrelated to biology, specifically material science, use sampling to establish and quality control industrial processes, such as the manufacture of plastics, amalgams and composite materials. Dissection of such materials, followed by various chemical analyses, is used to determine the spatial uniformity of various parameters, such as density, polymer crosslinking, reaction completion, etc.
Currently, microdissection of biological tissues is performed using laser based dissection systems. In one approach known as laser capture microdissection (LCM) (U.S. Pat. No. 6,010,888), a film of plastic is placed over a tissue section mounted on the stage of a microscope. When a region to be microdissected is located in the microscope field, a laser is focused on this region. The laser melts the plastic film over the region of interest, the plastic flows upon the region of interest and solidifies, essentially “gluing” the region of interest to the plastic film. When the film is removed from the tissue section, it carries with it the region of interest.
In another laser-based application, as described, for example, in U.S. Pat. No. 5,998,129, referred to herein as the “Catapult System”, a laser is used to cut the slide upon which the tissue is affixed, thereby releasing the region of interest from the rest of the slide and tissue section. The cut piece is propelled to an analysis location by means of light pressure from a laser pulse.
Another method for tissue microdissection U.S. Pat. No. 5,843,644 describes the use of an adhesive-tipped probe.
A variety of methods and devices exist (e.g. U.S. Pat. No. 6,534,307) to prepare so called “tissue microarrays”. These are usually glass slides upon which are mounted some number of tissue disks cut from a cylindrical core of tissue. These devices use a hollow needle to extract a core of tissue from frozen blocks of tissue or chemically fixed tissue. These cores are imbedded in a block of waxy material, and sections of this block are mounted on the glass slide resulting in a tissue microarray.
U.S. Patent Application Publication No. US 2007/0141760 A1 describes a device for embedding electronic components in a support medium. The motivation for doing so is to fabricate electronic circuits. The publication does not anticipate such a process for isolating or dissecting materials for analytical purposes.
The throughput limitations of LCM and the Catapult System limit the kinds of analyses that can be performed. In many cases, the parts of a tissue section that are of greatest interest cannot be identified at all using prior art microscopy. For example, the part of a tumor that leads to metastatic disease usually cannot be identified using microscopy. Such a situation requires testing of different regions using the methods of molecular biology, and this must be done in a sampling mode, wherein many samples, perhaps thousands, are analyzed. If a tumor has high genetic variability throughout, for example, if there are a thousand genetically different regions within the same tumor, these cannot all be characterized using LCM or the Catapult System except with monumental effort and significant expenditure of resources, because it is very difficult, time consuming, and expensive to perform a thousand microdissections using these methods. Thus, a significant limitation is the need of an expert in tissue morphology, such as a pathologist or expert developmental biologist, who must interact with the instrument in real time (i.e. during the dissection process) to identify structures of interest prior to dissection. In cancer research, the participation of a pathologist is required, and competing demands on the clinical pathologist's time are often severe.
A second significant drawback of currently available devices, such as LCM or the Catapult System, is that more thorough microdissection of an entire tissue section of useful size, e.g. 1 millimeter square, up to 1 centimeter square, into pieces having a useful size, e.g. 10 micrometer square up to 1 millimeter square, is not practical for the prior art because of their low throughput. It is reasonable to perform 10-20 dissections in a single 8 hour session using LCM. The Catapult System is more flexible, allowing 96 separate samples to be collected automatically, once the desired structures are identified. The rate at which different structures can be identified will vary from operator to operator, but even assuming the improbably high rate of one identification per minute, only 5 runs (5×96=480 samples) could be completed in an 8 hr. work day using the Catapult System.
Furthermore, acquisition of additional samples from the same section in subsequent microdissection sessions requires additional setup time, including reorientation of the tissue sample in the dissection instrument, and reexamination of the sample by an expert. This also limits processing. Wherein samples that require a larger number of microdissected voxels, using existing methods or devices may be impractical.
Furthermore, another disadvantage of the LCM approach are that placement of the plastic film upon the tissue section is difficult to automate for high-throughput applications, and repeated placement of the plastic film on the same tissue section to acquire diverse samples from the same tissue section is likely to degrade the structural integrity of the tissue section.
Finally, currently available devices have no facilities to track these relative positions between sessions. The accumulation of damage to the sample, the potential of mixing up samples, as well as possible difficulties in orienting the sample consistently from session to session are impediments to existing methods and devices.
Therefore, a need exists for effective, high-throughput dissection device.